Diffusion vacuum pump



63 p. L. STEVENSON 3,075,687

DIFFUSION VACUUM PUMP Filed June 7, 1961 2 Sheets-Sheet 2 INVENTOR. DONALD LEE STEVENSON ,L- Z 51 1 1446! a. cw. ATTORNEY United States Patent 3,075,87 Dll FUglflN VACUUM PUMP Donald Lee Stevenson, 227 S. Clinton St, Albion, FLY. Filed June 7, 1961, Ser. No. 115,547 6 Claims. (Cl. 230-161) The present invention relates to diffusion high vacuum pumps and, more particularly, to an improved nozzle assembly construction for this type of pump.

Diffusion pumps for producing high vacuum are Well known. Such pumps operate on the principle tlllt a l'quid having relatively heavy molecues is vaporized in the pump by raising the liquid temperature. The vapor comprising heavy molecules is directed by suitable nozzles in a direction away from the region to be evacuated, towards a mechanical forepump. The accelerated molecules of vapor collide against molecules ahead of the nozzle, forcing them toward the mechanical forepump and thereby reducing the pressure within the evacuated region. The vapors are recondensed on a cool wall of the pump Where the liquid is permitted to return to the bottcm of the pump to be reheated and vaporized.

In diffusion pumps of medium and large size, it has been the general practice to weld or braze the nozzle sections to each other and supporting structures or the nozzle assembly is fabricated. The resultant arrangement is unitary, that is, comprises a single fabricated body which must be installed or removed from a pump casing while all nozzle stages are secured. For extra large dtfusion pumps, this procedure for moving nozzle assemblies is rather cumbersome and sometimes leads to damaged assemblies which may be jarred or inadvertently bumped against the sides or ends of the pump casing.

Another disadvantage in the welded unitary nozzle assembly is the inconvenience and cost necessitated by replacement to any particular nozzle section in the event such section is damaged or worn. During fabrication of the conventional nozzle assemblies, there is always the problem of maintaining concentricity and alignment of the sections during the arrangement thereof. In addition since these parts are made of light gauge metal components, the chances of bending or flexing them out of shape during welding is great. Therefore, it is the principal object of the present invention to provide a novel and improved nozzle assembly for a difiusion pump which will aileviate the problems and disadvantages enumerated above.

The present invention is particularly adapted for diffusion pumps of large size, however, it is also adapted for small and medium sized pumps. There is provided a plurality of stepped radially positioned fins projecting from a cylindrical member arrsnged within the nozzle assembly of the pump. The fins are stepped on their own edges so that there is a succession of treads and risers on each of the fins. Each nozzle section of the azsembly is associated with corresponding pairs of treads and risers of the fins.

A principal object of the present invention is to provide a novel and improved vapor operated diffusion pump.

Another object of the invention is to provide a novel nozzle assembly for a diffusion pump having relatively large size both in diameter and in height.

Still another object of the invention is to provide a novel nozzle assembly which may be easily disassembled and mounted within and removable from a diffusion pump casing thereby rendering fabrication and replacement of separate parts of the pump rather easily.

Other objects and advantages will become apparent from the following specification taken in conjunction with the accompanying drawing wherein:

FIGURE 1 is a side elevational view partially in sec- 3,075,687 Patented Jan. 29, 1963 tion, of a diffusion pump incorporating the improved nozzle assembly of the present invention;

FIGURE 2 is a plan view, partly in section, of the noz- Zle assembly shown in FIGURE 1; and

FIGURE 3 is a perspective view of the support fins for the nozzle assembly.

Referring to the form of the invention as shown in FIGURE 1, the numeral ltl indicates generally the housing of the diffusion pump which includes a hollow cylindrical casing 12 with an integral bottom wall 14. The bottom wall 14 may be brazed, welded or otherwise secured to the bottom edge of the hollow cylindrical casing 12 in order to provide a hermetic seal therebetween.

The upper end of the pump is provided with a suitable inlet flange 16 to which a cooperating flange forming a part of the system being evacuated may be secured. The inlet to the pump is provided with a centrally located opening 18 through the flange 16 and communicates with the interior of the housing 10. The discharge side of the pump is provided with a pipe 19, one end of which opens into the lower portion of the casing 12.

The interior of the pump includes a nozzle assembly indicated generally at 20. The nozzle assembly combines a hollow central sectional nozzle stack having overlapping sections forming annular downwardly directed orifices, such as indicated at 22, 24, 26 and 28. Vapors rising in the center space of the nozzle assembly 20 are directed out of the respective orifices in downwardly directed nozzles. The level of oil in the bottom of the pump is indicated by the numeral 36. The interior surface of the casing 12 condenses the vapors which are directed downwardly out of the nozzle orifices and the resulting oil droplets run down the wall of the casing 12 and into the oil charge.

The heater assembly, generally indicated by the reference numeral 36 to which the present invention is particu'arly associated, is located on the bottom wall 14 in the lower end of housing 10 and is utilized for heating the liquid charges therein and generating vapors for operation of the pump nozzles. The bottom wall 14 is preferably formed with a centrally disposed dome 3% which may occupy a substantial area of bottom wall thereby redu:ing substantially the amount of pump fluid needed for full operation of the pump.

The heater assembfy 36 comprises a pair of concentric annular heater rings 39, 40 arranged coaxially of the housing 12 and adapted for electrical energization by a suitable electric source, not shown. The heater assembly 35 is described and illustrated in detail in the United States copending application Serial No. 94,727, filed on March 10, 1961, and assigned to the same assignee as is the present invention. Since the particular heater assembly forms no part of the present invention, further description thereof will be unnecessary. It is to be understood that the particular heater assembly 36 is utilized in the present description only for illustrative purposes and that any other suitable heater arrangement may be utilized with the present invention.

Arranged above the heaer assembly 36 and the dome 38 is a nozzle assembly supporting frame generally indicated by the reference number 40. The frame comprises a plurality of radially extending plates 42 having inner straight edges 44 secured in spaced relation around the periphery of a support cylinder 46. The outer edge of each of the plates 42 is formed in a plurality of step-wise ascending pairs of treads and risers which support individually, the orifice structures of the nozzle assembly. As shown in FIGURES 1 and 3, each plate 42 is formed with a first tread edge 48 and first riser edge 59, a second tread edge 52 and second riser 54 and a third-tread edge 56 and third riser 57 and a fourth tread edge 58 and fourth riser 59. In order to maintain the plates 42 in a fixed angular spaced arrangement and to enhance the rigidness of the frame, a metal circular band 60 connects all of the plates 42 along a suitable shoulder 62 of a projecting tongue 63 formed on the tread edges 48 at the upper end of the plates. Another circular metal band 64 connects the plates along a shoulder 66 formed at theslower end of each of the plates.

The frame 40 in assembled condition is shown in FIG- URE 3 and is illustrated as having eight plates 42 arranged radially of the support cylinder 46. The angles between plates preferably are equal and any suitable number of plates may be utilized; The assembled frame 40 may be lowered into the hous'ing 12 of the pump and means are provided for accomplishing this, as shown in FIG- URE 1. To this end, the interior of the supporting 'cylinder 46 is provided wi'th' a' transverse wall 68 intermediate the ends thereof and. a rod. 70 is slidably mounted in the cylinder through a suitable aperture '72 formed centrally of the wall .68. A restraining plate 74 is secured at the lower end of the rod 70 so that upon vertical movement of the rod 70, the plate 74 will engage the lower surface of the wall 68 so that further vertical movement of the rod will carry therewith the entire frame 40. An eye 76 formed on the upper end of the rod70 cooperates with a book 78 of a shaft 80 which, in turn, may be secured to the cowl 82 of uppermost firststa'ge orifice 22 of the nozzle assembly. 7 It will be apparent that in order to extract the frame 40 from the pump housing, an operator need only remove the cowl 82 from its customary operative position and lift the shaft 80 upwardly until the eye 76 of the rod 70 is in position for handling. The rod 70 may be moved upwardly manually or by a suitable lift mechanism, depending upon theweight of the nozzle assembly and supporting frame 40; I

The structure of the orifices that go to make up the nozzle assembly 20 are detachably mounted on the frame 40 and may be individually placed upon the frame at a corresponding position thereof. The first stage orifice 22 comprises the first stage cowl 82 and a cooperating orifice rim 86 and, as previously mentioned, thercowl 82 is attaehed to the shaft 80. Suitable spacers 84 connected to the rim 86 detachably support the cowl 82 thereon and the weight 'ofthe elements 70, 74, 82 maintain the cowl 82 in position. The first stage rim 86 isformed at the upper end of the first stage chimney 88 which supports, at its lower end, the cowl 90 of the second stage orifice 24. The chimney 88 'is supported on the edges 48 of the plates 42 and encircles the shaft 80 for supporting the same and the cowl 82.

Cooperating with the cowl 90 and forming part of the second stage orifice 24 is a second stage rim 92 which forms the upper end of the second stage chimney 93. This chimney fits around the riser edges 50 of the plate 42 and is supported on the tread edges 52 of these plates. Attached to the lower end of the chimney 93 is a third stage cowl 94 which cooperates with a third stage rim 96 to form the third stage orifice 26. The rim 96 forms the upper end of the third stage chimney 98 which in turn is supported on the tread edges 56 of the plates42 and engages the riser edges 54. At the lower end of the chimney 98 there is secured the fourth stage cowl 100 which together with a rim 102 form the fourth stage orifice 28. The rim 102 forms the upper end of a fourth'stage chirnney 104 which has secured at its lower end the skirt 106 of the nozzle assembly'20. The chimney 104 and consequently the rim 102 and skirt 106 are. suported on the tread edges 59 of the plates 42 by means of a ring 108 which is secured on the inner surface of the chimney 104 and engageablewith the tread edges 59.

The chimney 104closely fits around the riser edges 59 of the plates 42 and has formed at spaced points along the skirt 106 'a pl urality of projections 109 which are adapted to engage theinner'surface' of the pump casing 12 In this manner, the fourth or lowest stage of the nozzle assembly maybe centered relative to-the pump c a sing 4 and serve as the primary centering means for the assembled nozzle assembly.

The centering of the fourth stage chimney 104 by the projections 109 also serves to center the frame structure 40 and this is accomplished by the cooperation of the chimney 104 with the riser edges 59. A plurality of circumferentially arranged spacers 110 secured to the fourth stage rim 102 serves to maintain the cooperating fourth stage cowl 100 at a proper orifice spacing therefrom and also to adjust the cowl 100 relative to the rim 102. Similarly, a plurality of circumferentially arranged spacers 112 secured to the third stage rim 96 serves to maintain the proper cooperating third stage cowl 94 at a proper orifice spacing therefrom and also to adjust the cowl 94 relative to the rim 96.

Continuing upwardly, a plurality of spacers 114 are secured to the second stage rim 92 and serve to space the second stage cowl therefrom a proper distance for pump operation and to adjust the cowl relative to the cooperating rim.

The skirt 106, chimney 104 and the rim 102 are secured together by any suitable means such as by welding or brazing to form a complete individual unit which is placed around the frame structure 40 and lowered to the position shown in FIGURE 1. Vertical positioning of this unit is determined by the engagement of the ring 108 upon the tread edge 58. Centering of this unit relative to the pump housing is accomplished by the projections 109 and relative to the frame .struc ture'40 by the engagement of the chimney 104 and the riser edges 59.

The cowl 100, chimney 98 and the rim 94 are secured together by any suitable means to form another complete individual unit which is placed around the frame '40 and lowered until the cowl engages the spacers and the lower end of the chimney engages the tread edges 56. Centering of this unit is accomplished by the abutment of the chimney 98 with the riser edges 54.

Similarly, the cowl 94, chimney 93 and the rim 92 are secured together to forma third unit which is arranged above the chimney 98 and is lowered until the lower end of the chimney 93 abuts the tread edges 52 and the cowl 94 engages the spacers 112. Centering of this unit is accomplished by the abutment of the riser edges 50 upon the inner surface of the chimney 93.

The cowl 90, chimney 88 and the rim 86 are also joined together to form a fourth complete unit of structure and this 'unit rests upon the tread edges 48 and is centered relative to the frame by the engagement of the ring 60 with the shoulder 62 of the tongue 63.

In order to disassemble the nozzle assembly 20, the fourth unit is first removed simply by lifting the same and this procedure is followed for the third, second and first units. In the event it is desired to remove the entire nozzle assembly from the pump, the operator need only lift the rod 70 vertically to thus lift the frame 40 out of the housing of the pump. Lifting of the frame would carry therewith the four units which go to make up the orifice structure. Each orifice may then be removed individually and assembled in this manner in the event that one or. more has been damaged or worn.

I claim:

1. A diffusion pump comprising a cylindrical casing having a bottom wall; a heater assembly positioned ad'- jacent the bottom wall for boiling the pump fluid; a frame structure comprising a cylindrical member arranged coaxially within and relative to the casing, a plurality of plates each secured along an edge to said member and projecting outwardly therefrom, each of-said plates being formed along their outer edge with a plurality of stepwise ascending pairs of treads and risers; and a nozzle assembly including an annular nozzle section operatively connected with each of said pairs of forming annular downwardly directed orifices spaced axially within the casing.

2. A diifusion pump comprising a cylindrical casing having a bottom wall; a heater assembly positioned adjacent the bottom wall for boiling the pump fluid; a frame structure comprising a cylindrical member arranged coarially within and relative to the casing, a plurality of plates each secured along an edge to said member and projecting outwardly therefrom, each of said plates being formed along their outer edge with a plurality of stepwise ascending pairs of treads and risers; and a nozzle assembly including an annular nozzle section detachably mounted upon the treads of said pairs for forming annular downwardly directed orifices spaced axially within the casing.

3. A difiusion pump comprising a cylindrical casing having a bottom wall; a heater assembly positioned adjacent the bottom wall for boiling the pump fluid; a frame structure comprising a cylindrical member arranged coaxially within and relative to the casing, a plurality of plates each secured along an edge to said member and projecting radially outwardly therefrom each of said plates being formed along their outer edge with a plurality of alternately generally vertical and horizontal edge portions disposed in step-wise arrangement wherein successive upper vertical edge portions are closer to said member than the preceding lower vertical edge portion; and a nozzle assembly comprising a plurality of pairs of concentric annular sections which cooperate to form an annular orifice for the flow of diffusion vapors, each of said pairs of annular sections mounted on adjacent vertical and horizontal edge portions.

4. A diffusion pump comprising a cylindrical casing having a bottom wall; a heater assembly positioned adjacent the bottom Wall for boiling the pump fluids; a frame structure comprising a cylindrical member arranged coaxially within the casing, a plurality of plates each secured along m edge to said member and projecting radially outwardly therefrom, each of said plates being formed along their outer edges with a plurality of stepwise ascending pairs of treads and risers; and a nozzle assembly having a plurality of nozzle orifices, each of said orifices including a cowl section and an orifice rim section, said nozzle orifices being arranged upon said plates such that a rim section of one of said orifices and a cowl section of another orifice are mounted on the same corresponding tread of each of said plates.

5. A diffusion pump comprising a cylindrical casing; a bottom wall; a heater assembly positioned adjacent the bottom of the casing for boiling the pump fluid; a frame structure comprising a cylindrical member arranged coaxially within and relative to the casing, a plurality of plates each secured along an edge to said member and projecting radially outwardly therefrom, each of said plates being formed along their outer edge with a plurality of alternately generally vertical and horizontal edge portions disposed in step-wise arrangement wherein for each plate the successive upper vertical edge portions are closer to said member than the preceding lower vertical edge portion; and a nozzle assembly having a plurality of nozzle orifices each of which comprises an annular cowl section and an annular rim section, one of said cowl sections being mounted coaxially to said member on one horizontal edge of each of said plates, another of said cowl sections being mounted coaxially to said member on another horizontal edge of each of said plates.

6. A dillusion pump comprising a cylindrical casing; a bottom wall; a heater assembly positioned adjacent the bottom of the casing for boiling the pump fluid; a frame structure comprising a cylindrical member arranged coaxially within and relative to the casing, a plurality of plates each secured along an edge to said member and projecting radially outwardly therefrom, each of said plates being formed along their outer edge with a plurality of alternately generally vertical and horizontal edge portions disposed in step-wise ararngement wherein for each plate the successive upper vertical edge portions are closer to said member than the preceding lower vertical edge portion; and a nozzle assembly having a plurality of nozzle orifices each of which comprises an annular cowl section and an annular rim section, one of said rim sections being mounted coaxially to said member on one vertical edge of each of said plates, another of said rim sections being mounted coaxially to said member on another vertical edge of each of said plates.

No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3 075 687 January 29 1963 Donald Lee Stevenson It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant lines I to 3 for Donald Lee Stevenson of Albion New York;' read Donald Lee Stevenson of Albion New York assignor to Consolidated Vacuum Corporation of Monroe County New York a corporation of New York line 12 for "Donald Lee Stevenson his heirs read Consolidated Vacuum Corporation its successors in the heading to the printed specification line 3 for Donald Lee Stevenson 227 S., Clinton Ste Albion NO Yg" read Donald Lee Stevenson assignor to Consolidated Vacuum Corporation Monroe County N0 Y 9 a corpo ration of New York Signed and sealed this 1st day of October 19630 I (SEAL) Attest:

ERNEST W. SWIDER DAVID L LADU Attesting Officer Commissioner of Patents 

1. A DIFFUSION PUMP COMPRISING A CYLINDRICAL CASING HAVING A BOTTOM WALL; A HEATER ASSEMBLY POSITIONED ADJACENT THE BOTTOM WALL FOR BOILING THE PUMP FLUID; A FRAME STRUCTURE COMPRISING A CYLINDRICAL MEMBER ARRANGED COAXIALLY WITHIN AND RELATIVE TO THE CASING, A PLURALITY OF PLATES EACH SECURED ALONG AN EDGE TO SAID MEMBER AND PROJECTING OUTWARDLY THEREFROM, EACH OF SAID PLATES BEING FORMED ALONG THEIR OUTER EDGE WITH A PLURALITY OF STEP- 